Which density-dependent factor tends to occur when population size is high, such as disease?

Which density-dependent factor tends to occur when population size is high, such as disease?

• A. Predation
• B. Parasitism
• C. Disease
• D. Competition

Answer: (C)

In density-dependent regulation, the impact of the factor increases as population size grows. Disease fits this pattern because transmission depends on how often individuals come into contact. When there are many individuals in a given area, contact rates rise, so pathogens spread more readily, causing higher mortality or lower reproduction. This stronger effect at high density naturally slows population growth and can help stabilize or reduce numbers as density increases. Weather or other density-independent factors affect populations regardless of how many individuals are present, so they don’t scale with population size. While predation, competition, and parasitism can be density-dependent in some contexts, disease is the clearest and most direct example of a density-dependent factor that intensifies with higher population density.

In density-dependent regulation, the impact of the factor increases as population size grows. Disease fits this pattern because transmission depends on how often individuals come into contact. When there are many individuals in a given area, contact rates rise, so pathogens spread more readily, causing higher mortality or lower reproduction. This stronger effect at high density naturally slows population growth and can help stabilize or reduce numbers as density increases. Weather or other density-independent factors affect populations regardless of how many individuals are present, so they don’t scale with population size. While predation, competition, and parasitism can be density-dependent in some contexts, disease is the clearest and most direct example of a density-dependent factor that intensifies with higher population density.